LAUSR

The force-controlled fast tool servo (FTS) is an innovative tool and demonstrated to be very promising for both the manufacturing and metrology of complex-shaped surfaces. Facing challenges in developing a force sensing FTS (FS-FTS), a novel piezo-actuated FS-FTS is developed without using external force sensors. Unlike the disturbance observer based force self-sensing, a mechanical observer is deliberately designed to provide an exact estimation of the actuation dynamics and nonlinearity. Moreover, through arranging the actuation and force sensitive end in different places in the flexure chain of the FS-FTS, the conflict between the force sensing resolution and the working bandwidth can be well resolved, providing an opportunity to simultaneously achieve a high working bandwidth and a high force sensing resolution. Assisted by an established element-node model, the dependence of the FS-FTS performance on its structural parameters is derived, and accordingly, the structure is optimized through a Pareto frontier based multiobjective optimization, which is then verified via the finite element simulation. The experiment result suggests that the obtained force sensing resolution and bandwidth are about 0.24 mN and 600 Hz, respectively. Finally, a hybrid position/force control is realized by employing a generalized impedance model.